Flat mail, or "flats" are terms used to refer to mail other than normal letter-sized envelopes, and includes magazines, oversized envelopes, and thin mailer sheets which are folded over in half, thirds, or quarters, and fastened by a staple, tape or adhesive. Presently, such mail requires a significant amount of handling by Postal Service personnel, due to the inability of commonly available automated mail handling equipment to quickly separate individual pieces of flat mail for reading and subsequent sorting.
Flats, as well as letter-sized envelopes, are usually fed in horizontal stacks of vertically oriented pieces to automated machinery, which separates or singulates individual pieces from the stack, positions each piece for manual or automatic reading of the Zip Code, and subsequent sorting of each piece to a bin corresponding to the Zip Code or a portion thereof, such as the last three digits. Regardless of whether the reading is done manually or automatically, the separation equipment must properly separate and position each document for fast and efficient reading without jamming. Also, the passage of "doubles", or two pieces temporarily stuck together, through the separation path is to be avoided.
Conventional equipment has the tendency to damage or mutilate flat mail during the separation process. Folded over pieces and magazine pages are often skewed and torn by being subjected to uneven conveyor roller or belt pressures, larger envelopes are often creased, crumpled or inadvertently folded, and smaller pieces sometimes temporarily adhere to larger ones.
Various systems have been proposed for providing trouble free and rapid automatic separation, singulation and sorting of flats. One such system is described in U.S. Pat. No. 5,257,777, incorporated by reference herein, and commonly owned by the assignee of this application. The described singulator uses a movable set of belts to frictionally engage one of the surfaces of an envelope within a shingled array of envelopes to separate and transport that envelope to a conveying path. The singulator also employs a set of hold back belts to frictionally engage and halt the advance of the other envelopes thereby allowing the separation. However, the frictional engagement to halt the advance of the other envelopes creates wear in the document separator which after the processing of large amounts of envelopes may impact the ability of the hold back belts to hold back the remainder of the envelopes. In addition, particularly when high volume separation is occurring, residue has a tendency to be deposited on the hold back belts by the envelopes. This residue may reduce the ability of the hold back belts to frictionally engage the other documents to halt their advance.
Thus, there is a need for an apparatus which rapidly separates and singulates flat mail with a relatively simple yet cost effective configuration. There is also a need for such an apparatus which grips mail pieces of all sizes over a substantial surface area of each piece for rapid transmission along the separation path to prevent crimping of the mail piece. There is also a need for such a separator which accommodates pieces of flat mail of varying thicknesses, from thick magazines to single sheets, without jamming. There is a further need for a flat mail separator which is capable of separating as many as 10,000 pieces of mail per hour and accommodating the wear that such a high volume may create.